The other method is using a variometer (inductive), which is easier than making a variable capacitor:

http://www.crystalradio.net/crystalsets/hassell/index.shtml

Newpaper will be 'fun' to work with as its moisture content will vary with environmental conditions, making its dielectric constant not very..erm..constant - unless you impregnate it with wax or a lacquer.

(Made plenty of crystal sets during my teen years in the mid 70s-80s)